Key Geochemical Factors during Supercritical CO2-related Subsurface Operations

Abstract:

A deeper understanding of the impacts of brine−mineral interactions on supercritical (sc) CO₂-enabled subsurface operations is critical for designing safer and more effective technologies. In this talk, using a Fe-containing phyllosilicate model, I will first discuss effects of various subsurface-abundant inorganic and organic aqueous species on dissolution and precipitation of minerals and their subsequent change in mineral surface wettability. Then, I will explain how these newly experimentally obtained insights can be useful for subsurface and environmental deployment. During this talk, a specific example system will be introduced: brine-biotite (Fe-containing phyllosilicate) reactions under 95 °C and 102 atm of CO₂, which is a relevant condition to geologic CO₂ sequestration and scCO₂-enhanced energy recovery/storage processes. The effects of diverse brine chemistries including potassium, sodium, sulfate, phosphate, acetate, oxalate, and phosphonate on chemical and physical property changes of biotite minerals were examined using aqueous chemistry, interfacial chemistry, and solid phase analyses. We found that while sulfate, acetate, and oxalate did not promote secondary mineral formation, phosphate and phosphonates significantly promoted secondary precipitation of Fe- and Al-bearing minerals. In addition, the types and concentrations of ligands in the subsurface systems altered the surface wettability of minerals. This study provides useful geochemical insights into more efficient and safer geologic CO₂ sequestration and supercritical CO₂-enabld energy recovery/storage processes.